Selector switch for automatic telephone systems



Nov. 7, 1950 H. N. NEWSTEDT 2,529,409

SELECTOR SWITCH FOR AUTOMATIC TELEPHONE SYSTEMS Filed Aug. 24, 1946 ATTORNEY mEbu Ew Patented Nov. 7. 1950 SELECTOR SWITCH FOR AUTOMATIC TELEPHONE SYSTEMS Harry N. Newstedt, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application August 24, 1946, Serial No. 692, 883

8 Claims.

This invention relates in general to selector switches in automatic telephone systems, and more particularly to a novel circuit arrangement for a battery searching selector switch.

The object of this invention is to provide a novel controlling circuit which enables automatic selecting operations at maximum speed and with a high degree of accuracy, and to generally simplify and improve the circuit operation. Other objects and features of the invention will become apparent upon reference to the specification and accompanying drawing.

Referring now to the drawing, the automatic telephone system illustrated incorporates therein the wipers l1, l8, and I 9 opposite a desired group of bank contacts connected by trunk lines to connector 4 and thence to subscriber 5. Essentially the battery searching selector circuit consists of a well known Strowger vertical and rotary switch having off normal springs 9|, 92, and 93 and cam springs HM and H12 used in conjunction with a circuit including a line relay II], a holdv relay 20, a changeover relay 30, a stop relay 4!), a vertical magnet 50, a motor magnet or a rotary magnet 60, a stepping relay or a rotary pulsing relay 10, release magnet 80, their associated contacts and connections.

For explanatory purposes, it will now be assumed that calling subscriber l wishes to extend a connection to subscriber 5. On removal of the 7 receiver, a connection is initiated through finder 2 in a well known manner over conductors B, 1,

.and 8 to selector 3. Assuming that selector 3 is not busy, a circuit is completed for line relay [0,

which energizes and completes a circuit for relay 20 from ground over contacts 43 and H. Relay 20 energizes and at contacts 2| prepares a circuit forthe vertical stepping magnet 50, at contacts 22 breaks a point in the circuit to release magnet 80, at contacts 23 places ground on conductor 8 to maintain finder 2 operated and prepares a circuit for rotary pulsing relay through the off normal springs 93 which are open at this point and completes a circuit to changeover relay 30 from ground over contacts 23 and off normal springs 92. Relay 20 closes a further point in the rotary pulsing relay circuit at its contacts 24 and at contacts 25 applies ground to the battery searching wiper [9 through the winding of relay 40. Relay 30 is energized and at its contacts 31 opens a point in the circuit for rotary magnet and at contacts 32 closes another point in the circuit for vertical magnet 50. The selector is now prepared for the transmitted impulses from subscriber I, relays I0, 20, and 30 being in the energized condition.

On receipt of the break of the first impulse line relay I0 deenergizes and relays 20 and 30, having slow to release characteristics, remain operated for the series of impulses. Line relay In at its contacts H breaks the operating circuit to relay 20 and at its contacts l2 completes a circuit from ground over contacts 43, I2, 2|, and 32 to the vertical magnet 50 and the lower winding of relay 30'. In operating the vertical magnet 5|] elevates the wipers ll, 18, and I9 one step whereby they are positioned in the well known manner opposite the first level of bank contacts in the associated contact field. Assuming a series of five impulses were sent as the first digit by subscriber l, the wipers will be operated to a position opposite the fifth level of bank contacts in the associated contact field. Incident to the first vertical step of the wipers in response to the first operation of vertical magnet 50, the vertical 01f normal springs 92 are opened and springs 9| and 93 are closed. The springs 92 open the operating circuit of changeover relay 30 which now holds over an operating circuit from ground over contacts 43, I2, 2| and 32. The 01f normal springs 9| prepares a circuit for the release magnet and the 01f normal springs 93 completes a circuit for changeover relay 10 from ground over contacts 23, off normal spring 93 contacts 42 and 24, cam springs lfll and contacts 6|. Relay l0 operates and at contacts H short circuits the cam springs llll in its operating circuit and at contacts l2 prepares a circuit for rotary magnet 60.

At the end of the first digit dialed by subscriber l, relays l0 and 2|] are maintained energized and relay 30 after a short interval releases, its holding circuit being broken by relay In at its contacts l2. Relay 3!) on restoring, breaks the operating circuit for vertical magnet 50 at its contacts 32, and its contacts 3| energizes the rotary magnet 60 from ground over contacts 3| and I2. Rotary magnet 60 energizes and operates to rotate the Wipers ll, l8, and I9 into engagement with the contacts forming the first contact set of the fifth level selected by the vertical magnet. Rotary magnet 60 on energizing interrupts the operating circuit for rotary pulse relay l0. Relay 10 re- 3 leases and at contacts ll further breaks its own operating circuit, and at contacts 12 opens the operating circuit for magnet 6|]. Contacts 6| of rotary magnet 60 reclose the operating circuit for relay 18 from ground over contacts 23, off normal springs 93, contacts 62 and 25, cam springs ml and contacts 6|. The succeeding operations are dependent upon the idle or busy condition of the first connector thus selected in the selected group of connectors. If this connector is busy, the test conductor thereof terminating in the usual test bank contact accessible to test wiper I9 is marked with ground potential in the wellknown manner as indicated through the 'make contacts shown in connector 4 so that the upper winding of relay 4!] connected to the test wiper I9 is short-circuited to ground over contact 25. Relay l continues to operate as long as relay 4!] is not energized and at contacts I! closes its own holding circuit and at contacts 32 closes the aforetraced circuit for "rotary magnet 6!]. Rotary magrietGOfreoperates'and'advances the selector wipers a second step. The rotary step-by-step movement of the wipers'contiiiues until an idle connectoris located. In the event that no idle connecto'r is located, the wipers ll, 18 and 19 are driven step by step in aciockwise direction to the "eleventh stepwhereupon cam springs lOl are operated to the open position in a well known manner. "The opening 'of'cam springs Hll opens theenergizing circuit to'relay "i6 and prevents further operation of same. When a connector terminating in the bank accessible to Wiper I9 is idle, its test conductor is marked with negative battery potential in the well-known manner as indicated through thebreakcontacts shown in connector l. Assuming the selector hasengaged an idle connector, battery is connected-over the back coiftactin connector connector testconduotor, "the associated test bank contact, test wiper lfil, 'theupp'e rwi'nding of relay-40, contact 25 and ground. Relay "'40 "operates and arrests the trunkliunting operation bybreaking the previously tra'ced'operatingcircuit-to relay 79, which inturnprev'ents reoperationofrelay "it and con-' 93, contacts 23 'toground,atcontabtsiiopens the operating circuit for'slow=to=release relay 20 and release relay '8fi,'"and'a't contacts Handle disconnects the incoming connections of conductorsli and '1 to lin'e'relay ill and at contacts 45 andt'l connects the conductors through to wipers ll and l8to the'connector 4 selected, whereupon the relays therein correspondingtorelays Hi and 20in selector 3 energize to prepare the connector f4 for operation andto place a ground potential extending "from make contacts in connector *4,

as illustrated, to the test 'bank'contac't engaged by testwiper l9 similar to the manner in which relay 2!] in selector 3 places a ground on'con- -ductor 8 at "contacts 23. "after an interval and breaks the holding circuit Relay 28 deenergizes to finder Z-at its contacts 2-3. The finder 2 is now held'over contacts 48' and conductor 8 by the ground placed on wiper I9 by connector 4, and thestop relay GO -is held by the same ground over conductor l9, contacts 48, off normal springs 93, contacts 4| and the lower Winding of 'relay to. Relay 4D is therefore the only energized relay at-this time.

When the call is completed and the receivers replaced, ground is removed from conductor I 9 a "tacts.

by connector 4 whereupon relay 4!} and finder 2 release.

A circuit is completed from ground over contacts 43, I2, 22 and off normal springs 9| for release magnet 80, whereupon the restoration of the selector is brought about in the usual manner.

It will now be assumed that connector 4 is faulty to the extent that the connection from the test bank contact to the make-break springs, shown in connector 4, is open, due either to a break in the wire or to the accumulation of dust in between contacts included in the circuit leading to the test bank contact. In this case neither positive potential (ground), or negative potential (battery) is present on the associated test bank contact with the result that when test wiper l9 engages this test bank contact no circuit is completed for operating stop relay 4!] and therefore the wipers are stepped in the manner previously described to the next set of bank con- In this way a faulty connector is never seized "since the seizure of a connector requires the pressure of negative potentialon its associated test bank' contact. After stepping the Wipers beyond this faulty 'connector'the desired connection is completed in the manner previously described. i

l/Vhile a particular embodiment of theinv'ention has been describedit will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

1. In a selective switch 'havingcontacts'a test wiper, a motor magnet for'moving said test wiper over said contacts,said'contacts having negative battery potential thereon when idle and having positive battery potential thereon-When"busy,' an operating circuit for said motor magnet, a stepping relay, a circuit for operating said stepping relay, means for operating said stepping relay over said stepping relay circuit, contacts-closed by the operation of said stepping relay "for preparing the operating circuit of said magnet, means for completing said prepared operating circuit to operate said motor magnet to move said Wiper to engage the first one "of said contacts in search of anidle one, means operated by said motor magnet for openin the operating circuit of said stepping relay to release-the same, said stepping relay contacts operated in response to the release of said stepping relay 'to open the operating circuit of said magnet to release the same, said last means operated "in response to the release of said magnetto close theoperating circuit of said steppin'g'relay, a stop-relaya circuit completed for short'c irc'uiting said-stop'relay in case said wiper engages abu'sy bank contact having positive potential thereon, 'for energizin'g said stop relay in case said wiper engages an idle bank contact having-negativepotential therethereby prevent further operation of said stepping relay and said magnet.

2. In a selective 'switch-havingcontacts, a-test Wiper, a motor magnet for moving said test Wiper over s'aid'bank contacts, said bankc'ontacts having negative battery potential thereon whenidle and having positive battery potential thereon when busy, a stepping relay, a circuit for ope'r ating' said stepping relay,.means for controlling said stepping relay circuit to operate said stepping relay,v contacts controlled by the operation or said steppingrelay for operating said motor magnet to move said wiper to engage successive ones of said bank contacts in search of an idle bank contact, means operated by said motor magnet for opening the operating circuit to said stepping relay to release the same, said stepping relay contacts operated in response to the release of said stepping relay to open the operating circuit to said magnet to release the same, said last means operated in response to the release of said magnet to close the operating circuit of said stepping relay, a stop relay, a circuit completed for short circuiting said stop relay in case said wiper engages a busy bank contact having positive potential thereon, for energizing said stop relay in case said wiper engages an idle bank contact having negative potential thereon, and said circuit being ineffective to energize said stop relay in case said wiper engages a bank contact having neither positive nor negative potential thereon, contacts on said stop relay included in the operating circuit of said stepping relay for opening said stepping relay circuit in response to the operation of said stop relay to thereby prevent further operation of said stepping relay and said magnet.

3. In a selector having contacts, a test wiper, a motor magnet for moving said test wipers over said contacts, said contacts having negative battery potential thereon when idle and having positive battery potential thereon when busy, an operating circuit for said motor magnet, a stepping relay, a circuit for operating said stepping relay, means for operating said stepping relay over said stepping relay circuit, contacts controlled by the operation of said stepping relay for preparing the operating circuit of said magnet, means for completing said prepared operating circuit'to operate said motor magnet to move said wiper to engage the first one of said contacts in search of an idle one, contacts on said magnet included in the operating circuit of said stepping relay, a stop relay, a circuit completed for short circuiting said stop relay in case said wiper engages a busy bank contact having positive potential thereon, for energizing said stop relay in case said wiper engages an idle bank contact having negative potential thereon, and said circuit being inefiective to energize said stop relay in case said wiper engages a bank contact having neither positive nor negative potential thereon, contacts on said stop relay included in the operating circuit of said stepping relay, said stepping relay controlled by operation of said contacts on said stop relay and said contacts on said magnet.

4. In a selectively movable switch having contacts connected at times to negative battery potential and connected at other times to positive battery potential, a motor magnet for moving test wipers over said contacts, an operating circuit for said motor magnet, a set of off normal springs, a stepping relay, an operating circuit for said stepping relay, means for operating said off normal springs, said stepping relay operating circuit completed by the operation of said off normal contacts-in search ofan id1e;CQ aCt, .8; 101 relay) a circuit completed for short circuiting said stop relay in case said wiperengages a busy bank contact having a positive potential thereon, for energizing said stop relay in case said wiper engages an idle bank contact having negative potential thereon, and said circuit being ineffective to energize said stop relay in case said wiper engages a bank contact having neither positive nor negative potential thereon, contacts on said stop relay included in the operating circuitof said stepping relay, said contacts operated in response to energization of said stop relay to open said stepping relay operating circuit to thereby prevent further movement of said wiper.

5. A switch as claimed in claim 4in which said stop relay has a pair of windings, one of said windings being energized when said wiper is connected to said negative battery potential to operate said stop relay, and a circuit for the other of said windings completed by the operation of said stop relay for locking said relay operated.

6. In a selector switch having a wiper and contacts accessible thereto at times connected to negative battery potential, a line relay for the switch operated when the switch is seized and operated thereafter to operate said switch, a slow acting relay operated in response to the seizure of said switch and later released, a rotary magnet for moving the wiper over said contacts in search of a contact having said potential connected thereto, a circuit for said magnet, means controlled by the operation of said slow relay for opening said circuit, an interrupter relay for preparing the circuit of said rotary magnet operated after the slow relay is first operated, said icircuit completed by the release of said slow relay to start the operation of the rotary magnet, a circuit for the interrupter relay controlled by said magnet, said magnet and said interrupting relay interacting to step the wiper over the contacts.

7. In a two motion selector switch having a wiper and contacts accessible thereto at times connected to negative battery potential, a line relay for the switch energized when the switch is seized, a primary and a secondary operating magnet for said switch, a stepping relay, a slow acting relay, a circuit for said slow acting relay controlled by the initial energization of said line relay to thereby energize said slow acting relay, a circuit for said primary magnet prepared by the energization of said slow acting relay, a circuit for said secondary magnet opened by the energization of said slow acting relay, means responsive to an operation of said line relay to operate said primary magnet over the prepared circuit to thereby operate the switch in a primary movement, a set of off normal contacts operated when the switch is moved from its normal position, an operating circuit for said stepping relay closed by said oh? normal contacts, means responsive to the operation of said stepping relay to close a point in said circuit of said secondary magnet, said slow acting relay thereafter operated to open said circuit of said primary magnet and complete said prepared circuit to said secondary magnet, the switch thereby operated in a secondary movement.

8. A switch as claimed in claim 7 in which there is a means initially and continuously included in the said operating circuit of said stepping relay operated in response to an operation of said secondary magnet only after a definite number of operations of said magnet have occurred, said means effective to open the operating circuit of fii'l steppin -re'1ay and prevent energizaition o'f same.

'JHARRY -N. -NEWSTEDT.

H REFERENCES CITED "Thefollowing ref'er'ences are "of record in the file "of this "patent:

IiNI TED STATES P A*iiflI'IS Number Name Date Number 8 Name Date 'Stokely -'July 19,1932 Haines Sept. 2'7, 1932 Taylor NOV.22,11938 C1ark- Apr. 8, 1941 Ostline Mar. 30, 1943 Gray Dec. 14,1943 Christian Feb. 18, 1947 

